DCP darker than source file

[IMAXRestorationist]

Hello,

I am looking to create DCPs for shorts that were submitted as part of our school's amateur short film contest for projection at a cinema next month. I have been researching DCPs for the past few months and have worked as a hobby with video editing and color grading.

Most of our shorts were submitted with the H.264 codec, Rec.709 (Gamma 2.4 presumably), SDR and "Limited" Color range. I only have the free version of Resolve so I have tried different ways of creating a DCP:
1) Importing the H.264 file into DCP-o-matic and exporting the DCP directly
2) Importing the H.264 file into DaVinci Resolve and exporting as j2c stills. Gamma Tag was left on "Same as project" where the Output Color Space is Rec.709 Gamma 2.4. Then importing the image sequence into DCP-o-matic
3) Transcoding the file to DNxHR HQ using DaVinci Resolve, exporting as Rec.709 Gamma 2.4, then importing into DCP-o-matic selecting for Range once Rec.709 and another time Rec.1886. I guess here I should be choosing Rec.1886 if the source file is Gamma 2.4

For method 1) the output video has issues with playback in both VLC and DCP-o-matic player even though my PC can perfectly handle playback of official Hollywood trailer DCPs and even a feature DCP.
For methods 2) and 3) I am getting a darker image than the source file if viewed in VLC. I understand that the DCP is supposed to look different on my monitor but my understanding was that it would look brighter not darker.

I understand that the best way to test the output files would be in a theater but unfortunately I don't have access to one before the final projection. That's why I'm trying to figure out if there's any mistake in my process and if so, what's the best workflow for creating DCPs of videos for which I don't have the master files.

Also, I am assuming that the source file has a Gamma of 2.4, is there a way to verify that? My way of figuring it out is as follows: I export as Gamma 2.4 and if it matches the source file then that's the correct Gamma?

Finally, I'm unsure how to deal with the fact that the source files all have "Limited" Color range. I wouldn't want that to be cause an issue in either of the 3 methods.

I am using DCP-o-matic Version 2.16.78 and DaVinci Resolve 18.6.3 Build 19.
Thank you kindly for your help.

[StephW999]

Hello, you should use gamma 2.2 for rec709 on the resolve timelime, and export.
in DoM choose rec709 matrix.

You can also output directly in jpeg2000 dci with resolve, in image sequence (in a folder). When exporting, choose JPEG2000 format, and the Kakadu DCI Flat or Scope codec (depending on your project). in this case the setting in dom is to set the color matrix to “none” and choose import folder

[Carsten]

I think the safest way is to create the DCP in DCP-o-matic from the original rec.709 masters. DCP-o-matic will do anything necessary if you don't mess with the default settings. Limited range is the right option for rec.709 material. What is the frame rate of your source material? Are you creating the DCPs in 4k? If so, that is the reason for your playback problems, but these will not occur at the cinema.

Use a J2K bitrate in DCP-o-matic of not more than 200MBit/s.


You should also pay attention to audio levels - aim towards a loudness of around -20 LUFS or LEQ(m) around 80dB.



- Carsten